A systematic review and meta-analysis of comparative clinical studies on antibiotic treatment of brucellosis

Brucellosis is a difficult to treat infection that requires antibiotic combinations administered over several weeks for clearance of infection and relapse prevention. This systematic review summarizes current evidence for antibiotic treatment of human brucellosis. PubMed, EMBASE, Scopus, CINAHL, Web of Science, and China Academic Journal databases were searched for prospective studies that had compared different antibiotic regimens for treating human brucellosis in the last 25 years. Thirty-four studies recruiting 4182 participants were eligible. Standard dual therapy with doxycycline + rifampicin had a higher risk of treatment failure compared to triple therapy which added streptomycin (RR: 1.98, 95% CI 1.17–3.35, p = 0.01) or levofloxacin (RR: 2.98, 95% CI 1.67–5.32, p = 0.0002), but a similar or lower risk compared to alternative dual antibiotic combinations (p > 0.05). The same combination had a higher risk of relapses compared to triple therapy which added streptomycin (RR: 22.12, 95% CI 3.48–140.52, p = 0.001), or levofloxacin (RR: 4.61, 95% CI 2.20–9.66, p < 0.0001), but a similar or lower risk compared to other dual antibiotic combinations (p > 0.05). Triple antibiotic therapy is more effective than standard dual therapy with rifampicin and doxycycline. However, the latter is also efficacious and suitable for uncomplicated disease.


Objectives
4 Provide an explicit statement of the objective(s) or question(s) the review addresses.P5 Pa1 (The aim of…)

METHODS
Eligibility criteria 5 Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses.P5 Pa2 (Under subheading of study eligibility) Information sources 6 Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies.Specify the date when each source was last searched or consulted.
P6 Pa1 (Under subheading search strategy) Search strategy 7 Present the full search strategies for all databases, registers and websites, including any filters and limits used.P6 Pa1 (as above) and Supplementary Tabe 1 Selection process 8 Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.

P6 Pa2 (Under subheading data extraction and analysis)
Data collection process 9 Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.

P6 Pa2 (Under subheading data extraction and analysis)
Data items 10a List and define all outcomes for which data were sought.Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.
P5 Pa 2 (Outcomes assessed were..), Supplementary Table 2 -Characteristics of included studies 10b List and define all other variables for which data were sought (e.g.participant and intervention characteristics, funding sources).Describe any assumptions made about any missing or unclear information.

Study risk of bias assessment
11 Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.
P7 Pa 1 (under subheading risk of bias and certainty of evidence)

Section and Topic
Item # Checklist item Details of where the item is reported Effect measures 12 Specify for each outcome the effect measure(s) (e.g.risk ratio, mean difference) used in the synthesis or presentation of results.P6 Pa 2 (The effect size of each treatment comparison…) Synthesis methods 13a Describe the processes used to decide which studies were eligible for each synthesis (e.g.tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).
P5 Pa 2 (If two or more similar studies were available…) 13b Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions. P6

Study selection 16a
Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.
P7 Pa 2 (Thirty four studies published …) 16b Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.Supplementary  19 For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g.confidence/credible interval), ideally using structured tables or plots.
Tables 1 and 2 Results of syntheses 20a For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies.P8 Pa 3 under subheading Risk of Bias), Figure 2 20b Present results of all statistical syntheses conducted.If meta-analysis was done, present for each the summary estimate and its precision (e.g.confidence/credible interval) and measures of statistical heterogeneity.If comparing groups, describe the direction of the effect.

Supplementary Tables
Supplementary Table 1.Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.However, there is a high risk of reporting bias as though participants were followed up for relapses, the numbers are not reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures we did not include this "intermediate" outcome as a treatment failure in the meta-analysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).Karabay et al., 2004[15] The participants were randomly assigned but the allocation concealment was not mentioned (selection bias -intermediate risk).Open label study (performance bias -high risk) (detection bias -high risk).The attrition rate was more than 10% (attrition bias -high risk).Cure and failure rates are not reported (reporting bias -high risk).Follow up period is not specified, and the sample size was not met due to attrition (Other biases -high risk).
Blinding was not possible due to the differences in the duration of treatment (performance bias -high risk) (detection bias -high risk).The authors do not describe if all participants randomized completed follow up (attrition bias -unclear risk).
Total number of treatment successes and failures are not reported (reporting bias -high risk).Diagnosis and treatment success was not confirmed by culture (high risk of bias) Keramat et al., 2009[17] Randomized study but allocation concealment was not done (selection bias -high risk).The study was not blinded as some participants were treated for an extra 8 weeks (performance bias -high risk) (detection bias -high risk).The attrition rate was more than 10% (attrition bias -high risk).
Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is low as all outcomes assessed were reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the meta-analysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).
Liu et al., 2018 [19] Participant selection was randomized, but allocation concealment was not mentioned (selection bias -intermediate risk).
Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is high risk as the relapses were meant to be assessed but not reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the metaanalysis, but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).
Liu et al., 2019 [20] Participant selection was not randomized, and allocation concealment was not mentioned (selection bias -high risk).
Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is high risk as the relapses were meant to be assessed but not reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the metaanalysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).
Liu et al., 2021 [21] Participant selection was not randomized, and allocation concealment was not mentioned (selection bias -high risk).
Blinding was not possible due to study design (performance bias and detection bias -high risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is high risk as relapses were not reported.No other risks of bias.Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is low as all outcomes assessed were reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the meta-analysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).
The attrition rate was reported to be less than 10% (attrition bias -low risk).It is not clear if all enrolled participants were followed up until the completion of the study (reporting bias -unclear risk).Sample size calculation not mentioned, and infection was not confirmed with culture (Other biases -high risk).
Double blinded study (performance bias and detection bias -low risk), All participants are accounted for the outcome of cure (Attrition bias -low risk) .Reporting bias is high as relapses were not reported.No other risks of bias noted.
Zhang et al. 2022 [34] Participant selection was randomized, but allocation concealment was not mentioned (selection bias -intermediate risk).
Blinding is not mentioned (performance bias and detection bias -unclear risk), Low risk of attrition and reporting bias.
The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the meta-analysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).

Supplementary
of risk of bias for each included study.
Doxycycline, R -Rifampicin, S -Streptomycin, Co -Cotrimoxazole, G -Gentamycin, A -Amikacin, L -Levofloxacin, O -Ofloxacin, C -Ciprofloxacin) SF1.Comparison -D + R + S vs. D + R, Outcome -Treatment failure, Analysis -Per protocol (Figures for inten�on to treat analysis are included in main manuscript) SF2.Comparison -D + R + S vs. D + R, Outcome -Relapse, Analysis -Per protocol (Figures for inten�on to treat analysis are included in main manuscript) SF3.Comparison -D + R vs. C + R, Outcome -Treatment failure, Analysis -Inten�on to treat SF4.Comparison -D + R vs. C + R, Outcome -Relapse, Analysis -Per protocol (Figures for inten�on to treat analysis are included in main manuscript) SF5.Comparison -D + R vs. O + R, Outcome -Treatment failure, Analysis -Inten�on to treat SF6.Comparison -D + R vs. D + S, Outcome -Treatment failure, Analysis -Inten�on to treat SF7.Comparison -D + R vs. D + S, Outcome -Relapse, Analysis -Inten�on to treat SF8.Comparison -D + R vs. D + S, Outcome -Relapse, Analysis -Per protocol SF9.Comparison -O + R vs. D + S, Outcome -Treatment failure, Analysis -Inten�on to treat SF10.Comparison -O + R vs. D + S, Outcome -Relapse, Analysis -Inten�on to treat SF11.Comparison -D + R vs. D + C, Outcome -Treatment failure, Analysis -per protocol (Figures for inten�on to treat analysis are included in main manuscript) SF12.Comparison -D + S vs. D + G, Outcome -Treatment failure, Analysis -Inten�on to treat SF13.Comparison -D + S vs. D + G, Outcome -Relapse, Analysis -Inten�on to treat SF14.Comparison -D + R vs. D Outcome -Treatment failure, Inten�on to treat.

Table 3 Study
17aracteristics17Cite each included study and present its characteristics.P7 Pa 2 and Supplementary Table2

Table 2 .
Search strategy and results (last day of search -06/06/2023) Characteristics of Included Studies *Last date of search was 12/03/2024 for this resource Supplementary [32]randomized (selection bias -high risk), open label study (performance bias -high risk), with one arm receiving intravenous antibiotics (detection bias -unclear risk).The attrition rate was more than 10% (attrition bias -high risk).Randomized study but allocation concealment was not mentioned (selection bias -intermediate risk).Open label study with one arm having intravenous antibiotics (performance bias -high risk) (detection bias -high risk).The attrition rate was less than 10% (attrition bias -low risk).The cure rate and the therapeutic failure rate was not reported (reporting bias -high risk).Blood culture was not done for all suspected cases (Other biases -high risk).Roushan et al., 2004[77]Randomized trial with allocation concealment described (selection bias -low risk).Open label study (performance biashigh risk) (detection bias -high risk).The attrition rate was reported to be less than 10% (attrition bias -low risk).(reportingbias-highrisk).No sample size calculation provided and it is unclear if 2-ME titre was used to detect relapses (Other biases -high risk).Blinding is not mentioned (performance bias and detection bias -unclear risk), Attrition bias is low risk as all participants are accounted for the outcome of cure.Reporting bias is low as all outcomes assessed were reported.The study reports two categories of people as "cures" and "improved with treatment".Since the latter was not explicitly mentioned as failures, we did not include this "intermediate" outcome as a treatment failure in the meta-analysis but this introduces a high risk of bias in interpreting and reporting of the results (Other bias -high risk).Sofian et al., 2014[31]Randomized study but allocation concealment was not mentioned (selection bias -intermediate risk).Unblinded trial (performance bias -high risk) (detection bias -high risk).The attrition rate was reported to be less than 10% (attrition bias -low risk).No other risks of bias were identified.Solera et al., 2004[27]Randomized study but allocation concealment was not mentioned (selection bias -intermediate risk).The study was double blinded (performance bias -low risk) (detection bias -low risk).The attrition rate was more than 10% (attrition bias -high risk).Total cure and therapeutic failures were not mentioned (reporting bias -high risk).No other risks of bias were identified.Sun et al., 2020[32]Participant selection was randomized, but allocation concealment was not mentioned (selection bias -intermediate risk).
Roushan et al., 2010[25]Randomized study with allocation concealment described (selection bias -low risk).Unblinded study (performance bias -high risk) (detection bias -high risk).The attrition rate was reported to be less than 10% (attrition bias -low risk).No other risks of bias were identified.Roushan et al., 2006[12]Randomized comparative study with allocation concealment described (selection bias -low risk).No mention of blinding -study described as a comparatives study (performance bias -unclear risk) (detection bias -unclear risk).The attrition rate was reported to be less than 10% (attrition bias -low risk).All patients were accounted for including those not completing follow up (reporting bias -low risk).No other risks of bias were identified.

Table 5 .
Severe adverse events (SAE) reported in each study (only studies that reported SAE are shown)